Sliding cam system for an internal combustion engine

ABSTRACT

A sliding cam system for an internal combustion engine is disclosed. The sliding cam system includes a carrier shaft and an axially adjustable cam sleeve arranged on the carrier shaft. The cam sleeve is axially adjustable relative to the carrier shaft between a first axial position and a second axial position, and axially fixable in the respective axial position by a detent device. The detent device includes a first receiving groove assigned to the first axial position and a second receiving groove assigned to the second axial position. The detent device further includes a preload element disposed on the cam sleeve. The preload element preloads a detent element arranged between the carrier shaft and the cam sleeve towards the carrier shaft. The detent element is received in the first receiving groove in the first axial position and the second receiving groove in the second axial position.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to German Application No. DE 10 2021 204 314.3 filed on Apr. 29, 2021, the contents of which are hereby incorporated by reference in its entirety.

TECHNICAL FIELD

The invention relates to a sliding cam system for an internal combustion engine and to an internal combustion engine having at least one such sliding cam system.

BACKGROUND

So-called sliding cam systems with cam sleeves serve for controlling valves of an internal combustion engine. Often it is desirable to control the valve concerned with different cam profiles. For this purpose it is known to provide such a sliding cam system with a radially inner carrier shaft and with a hollow shaft, the cam sleeve, surrounding the carrier shaft on the outside, wherein carrier shaft and cam sleeve are formed so as to be axially adjustable relative to one another. Here, carrier shaft and cam sleeve are non-rotatably connected to one another so that from the driven carrier shaft a rotary movement and thus a torque can be transmitted to the cam sleeve with a cam profile. In this way, the valve is adjusted in each case via the cam profile interacting with the valve.

By axially adjusting the cam sleeve relative to the carrier shaft, the cam profile interacting with the valve can be changed. For this purpose it is known from the prior art to provide suitable adjusting devices for axially adjusting the cam sleeve between different axial positions, in which in each case a certain cam profile is in connection with the valve of the internal combustion engine.

It is known from conventional sliding cam systems for example to provide on the cam sleeve a slotted guide in which for axially adjusting the cam sleeve relative to the carrier shaft an engagement element can engage so that the rotary movement of the cam sleeve is also accompanied by an axial adjustment between the desired axial positions. As soon as the axial adjustment has been completed, the engagement element is again brought out of engagement with the slotted guide. Before this background it proves to be significant that an axial position of the cam sleeve, once firmly adjusted, is maintained relative to the carrier shaft in a reliable and stable manner for as long as no adjustment is desired. In order to ensure this, it is known from conventional sliding cam systems to secure the camshaft against undesirable axial movements relative to the carrier shaft with the help of suitable detent devices.

In conventional sliding cam systems, such a detent device includes a so-called ball-spring assembly, which is arranged in the carrier shaft and with which a ball is preloaded by means of a resilient component against a receiving groove provided in the cam sleeve, which is assigned to a certain axial position. This means that the substantial components of the detent device are provided in the carrier shaft that is arranged radially inside relative to the cam sleeve.

However, assembling this detent device proves to be relatively complicated. For example, the springs of the ball-spring assembly have to be held down to radially inside during the course of the assembly of the cam sleeve on the carrier shaft—which takes place by sliding on axially. Only then can the cam sleeve be axially slid onto the carrier shaft.

It is therefore an object of the present invention to provide an improved or at least alternative embodiment for the sliding cam system explained at the outset, which is characterised in particular in that it can be assembled particularly easily.

This object is solved through the subject of the independent patent claim and of the coordinated patent claim. Preferred embodiments are subject of the dependent patent claims.

SUMMARY

Accordingly, the basic idea of the present invention is, firstly, to provide the receiving grooves for receiving the ball of a ball-spring assembly explained above not on the sleeve-shaped cam sleeve but on the carrier shaft and, secondly, to provide the spring-ball element itself, i.e. the substantial component of the detent device on the cam sleeve arranged on the carrier shaft radially outside. This measure allows introducing the substantial components of the detent device into the cam sleeve from the outside. This can take place in particular after the cam sleeve has already been axially slid onto the carrier shaft. The disadvantageous holding-down of the springs of the ball-spring assembly while the cam sleeve is slid onto the carrier shaft explained above can thus be omitted. The result is that the assembly of such a sliding cam system is thus significantly simplified compared with conventional sliding cam systems. Apart from this, numerous standard parts such as for examples threaded pins, spring and ball and the likes can be made use of during the technical realisation of the solution according to the invention, from which the desired cost advantages materialise.

A sliding cam system according to the invention includes a carrier shaft extending along an axial direction, on which, radially outside and axially adjustable relative to the same, a sleeve-shaped cam sleeve comprising a cam profile is arranged. The carrier shaft and the cam sleeve together form a camshaft. Practically, the two shafts are arranged coaxially to one another. The carrier shaft and the cam sleeve can be or are non-rotatably connected to one another for the transmission of torque, preferentially by means of a tooth geometry. Here, the cam sleeve is axially adjustable between a first and at least one second axial position relative to the carrier shaft and can be fixed in the respective axial position on the carrier shaft by means of a detent device. According to the invention, the detent device includes a first receiving groove assigned to the first axial position and a second receiving groove assigned to the at least one second axial position, wherein the two receiving grooves each extend, axially spaced apart from one another, along an outer circumference of the carrier shaft, preferentially along the complete outer circumference. Further, the detent device includes a preload element present on the cam sleeve which preloads a detent element arranged between carrier shaft and cam sleeve towards the carrier shaft, wherein the detent element is received in the first receiving groove when the cam sleeve is located in the first axial position and is received in the second receiving groove when the cam sleeve is located in the second axial position.

According to a preferred embodiment, the preload element includes or is a preferentially resilient detent spring which is arranged in a receptacle present in the cam sleeve and exerts a preload force on the detent element. Such a detent spring is of a very simple design and thus reliable during the operation and additionally obtainable as standard part and thus cost-effectively available and in addition to this can also be easily assembled on the cam sleeve.

Practically, the receptacle is formed by an opening radially extending in the cam sleeve from the inner circumferential side of the same to the outer circumferential side, in which a support element is received. For generating the preload force the preload element supports itself on this support element radially outside. Since such an opening is accessible from the outer circumferential side of the cam sleeve, preload element, detent element and support element can thus be particularly easily assembled in the cam sleeve.

Particularly preferably, the opening can be formed as a through-bore. In this variant, the support element present in the through-bore is firmly connected to the cam sleeve by means of a press connection, in particular by means of a press fit and arranged fixed in place relative to the same. This variant is also of a particularly simple design technically and thus also particularly cost-effective in the production. Thus, reduced production costs materialise also for the entire sliding cam system.

In a further preferred embodiment, the support element comprises an external thread which, for the radial adjustability of the support element, engages in an internal thread provided on the opening formed complementarily to the external thread, so that the support element is radially adjustable relative to the cam sleeve. Thus, the preload force exerted on the detent element generated by the preload element supporting itself on the support element can be adjusted and thus optimised by adapting the radial position of the support element.

Practically, the support element can be formed as a threaded pin. A support element that is realistic as threaded pin is particularly simple in design and thus particularly cost-effective. Thus, cost-advantages in the production of the sliding cam system also materialise with such a threaded pin.

According to a further advantageous further development, a sleeve-shaped housing delimiting a housing interior can also be provided on the support element, in which the preload element and the detent element are each at least partially received. This facilitates the assembly of the preload element typically formed by a spring and also the assembly of the detent element on the cam sleeve. In particular, the preload element and the detent element, in this variant, can be initially preassembled on the support element and subsequently support element, detent element and preload element assembled in the cam sleeve as a unit.

Particularly practically, the support element, the preload element, the detent element and the sleeve-shaped housing can be formed integrally and thus as a unit. This variant can be particularly easily assembled on the cam sleeve so that the assembly of the sliding cam system is further simplified.

Particularly practically, the detent element can be designed as a detent ball. Such a detent ball is cost-effectively available as a standard part and additionally has a particularly suitable geometry for being received in a receiving groove.

According to an advantageous further development, the radius of the carrier shaft can be reduced in an axial region between the two receiving grooves. This facilitates the adjusting operation of the cam sleeve between the two axial positions since, during the axial adjusting, an enlarged radial intermediate space is thus available for the detent element or the detent ball.

According to a further advantageous further development, the at least two receiving grooves each comprise a groove base and a first and second groove flank, wherein the first groove flank has a smaller axial distance to the respective other receiving groove than the second groove flank. In this further development, the two groove flanks are each arranged in at least one receiving groove, preferentially in both receiving grooves, each at a first or second acute angle to the radial direction, wherein a first angular value of the first acute angle is greater than a second angular value of the second acute angle. Thus, the at least one receiving groove is axially provided towards the at least one other receiving groove with a flatter, i.e. less inclined groove flank, which simplifies disengaging the detent element or the detent ball out of the receiving groove for initiating the axial adjusting operation of the cam sleeve relative to the carrier shaft. Thus, only a reduced axial force is required in order to move the cam sleeve away, out of the first or second axial position.

According to a preferred embodiment, a radially measured depth of at least one, preferentially of all of the at least two receiving grooves amounts to maximally 10%, preferentially maximally 8% of the radius of the carrier shaft.

Further, the invention relates to an internal combustion engine for a motor vehicle having at least one cylinder comprising a combustion chamber. On the cylinder, an inlet valve for introducing fresh air into the combustion chamber and an exhaust valve for discharging exhaust gas out of the combustion chamber are provided. The motor vehicle, further, includes at least one sliding cam system according to the invention explained above for controlling the inlet and exhaust valve. The advantages of the sliding cam system according to the invention explained above thus apply also to the internal combustion engine proper.

Further important features and advantages of the invention are obtained from the subclaims, from the drawing and from the associated figure description by way of the drawings.

It is to be understood that the features mentioned above and still to be explained in the following cannot only be used in the respective combination stated but also in other combinations or by themselves without leaving the scope of the present invention.

Preferred exemplary embodiments of the invention are shown in the drawings and are explained in more detail in the following description, wherein same reference numbers relate to same or similar or functionally same components.

BRIEF DESCRIPTION OF THE DRAWINGS

It shows, in each case schematically:

FIG. 1 an example of a sliding cam system according to the invention in a longitudinal section along an axial direction of the carrier shaft,

FIG. 2 a further development of the example of FIG. 1, in which different components of the detent device that is substantial for the invention are formed as a unit in contrast with the example of FIG. 1,

FIG. 3 a detail representation of the sliding cam system of FIGS. 1 and 2 in the region of the two receiving grooves.

DETAILED DESCRIPTION

FIG. 1 illustrates an example of a sliding cam system 1 according to the invention in a longitudinal section. The sliding cam system 1 includes a carrier shaft 2 extending along an axial direction A on which, radially outside and axially adjustable relative to the same, a sleeve-shaped cam sleeve 3 comprising a cam profile 4 is arranged. Thus, the cam sleeve 3 is formed as a hollow shaft whose inner circumference 24 lies against the outer circumference 7 of the carrier shaft 2. Together, the carrier shaft 2 and the cam sleeve 3 form a camshaft.

The cam sleeve 3 extends along the axial direction A. The carrier shaft 2 and cam sleeve 3 are arranged coaxially to one another. The axial direction A extends along a common centre longitudinal axis M of carrier shaft 2 and cam sleeve 3. A radial direction R extends perpendicularly away from the centre longitudinal axis M and also away perpendicularly to the axial direction A. A circumferential direction U runs perpendicularly both to the radial direction R and also to the axial direction A round about the centre longitudinal axis M.

FIG. 1 shows the sliding cam system 1 in a longitudinal section along the axial direction A. Accordingly, for transmitting a torque from the carrier shaft 2 to the cam sleeve 3 the carrier shaft 2 and the cam sleeve 3 are non-rotatably connected to one another. The non-rotatable connection can take place for example, with a suitable tooth geometry, which on the inner circumference of the cam sleeve 3 and on the outer circumference of the carrier shaft 2 comprises projecting teeth in each case (not shown in the figures), which for transmitting a torque mesh with one another.

Irrespective of such a non-rotatable connection, the cam sleeve 3 is adjustable relative to the carrier shaft 2 along the axial direction A between a first and a second axial position AP1, AP2. In this way, the two cam profiles 3 a, 3 b formed on the cam sleeve 3 radially outside can also be axially adjusted. Apart from this, the cam sleeve 3 can be axially fixed in the respective axial position AP1, AP2 on the carrier shaft 3 by means of a detent device 5. In the example, the cam sleeve 3 has two different cam profiles 3 a, 3 b which are moulded on the cam sleeve 3 radially outside next to one another along the axial direction A. When the cam sleeve 3 according to the exemplary embodiment of the figures is located in the first axial position AP1, the first cam profile 3 a can interact with a valve of an internal combustion engine not shown in more detail in the figures. When the cam sleeve is located in the second axial position AP2, the second cam profile 3 b can interact with the valve of the internal combustion engine. Similar applies analogously also when three or more cam profiles and thus three or more axial positions of the cam sleeve 3 are provided.

Obviously, a larger number of such different cam profiles can also be provided in further developments of the example, wherein each cam profile is then assigned a certain axial position.

In the example of the figures, a first receiving groove 6 a and a second receiving groove 6 b spaced apart from one another are arranged on the outer circumference 7 of the carrier shaft 2 along the axial direction A as part of the detent device 5. Both run completely round about the outer circumference 7 of the carrier shaft 2 along the circumferential direction U. The first receiving groove 6 a serves for fixing the cam sleeve 3 in the first axial position AP1. The second receiving groove 6 b serves for fixing the cam sleeve 3 in the second axial position AP2. To this end, the detent device 5 includes a preload element 8 arranged on or in the cam sleeve 3, which preloads a detent element 11 arranged between carrier shaft 2 and cam sleeve 3 towards the carrier shaft 2, so that the detent element 11 is received in the first receiving groove 6 a when the cam sleeve 3 is located in the first axial position AP1 and received in the second receiving groove 6 b when the cam sleeve 3 is located in the second axial position AP2. The preload element 8 can be a detent spring 9 which is arranged in a receptacle 10 present in the cam sleeve 3 and exerts a preload force on the detent element 11. As shown, the detent element 11 can be formed as a detent ball 21.

The receptacle 10 in the exemplary scenario is formed by an opening 12 extending along the radial direction R from the inner circumference 24 to the outer circumference 25 of the cam sleeve 3. In the receptacle 10 or in the opening, a support element 13 is arranged on which the preload element 8 supports itself radially outside, so that it can exert the desired preload force on the detent element 11 radially inside.

In the example of FIG. 1, the support element 13 can be radially adjusted relative to the cam sleeve 3 along the radial direction R. To this end, the support element 13 comprises an external thread 16, which for the radial adjustability of the support element 13 engages in an internal thread 17 provided on the opening 12 formed complementarily to the external thread 16. Thus, the support element 13 can be moved along the radial direction R in the manner of a threaded pin 18.

FIG. 2 illustrates a further-development variant of the example of FIG. 1. In the example of FIG. 2, the support element 13 is followed radially inside by a sleeve-shaped housing 19 delimiting a housing interior 20. In the housing interior 20, the preload element 8 and the detent element 11 are at least partially received. Preferably, the sleeve-shaped housing 19 is dimensioned with respect to its diameter and matched to the diameter of the detent element 11 or the detent ball 21 so that the preload element 8, in particular the detent spring 9, is completely arranged in the housing interior 20 and the detent element 11 or detent ball 21 is arranged in the region of an opening edge 26, which surrounds a sleeve opening 27 of the sleeve-shaped housing 19 facing the carrier shaft 2. In this way, the guidance of the detent element 11 or of the detent ball 21 along the axial direction R is improved.

In a further development of the example of FIG. 2, the said elements, i.e. the support element 13, the preload element 8, the detent element 11 and also the sleeve-shaped housing 19 can be formed integrally and thus as a unit. Such a unit can be referred to as a “screwed-in resilient integral thrust piece”.

As is evident from FIG. 3, a radius r of the carrier shaft 3 can be reduced in an axial region 22 between the two receiving grooves 6 a, 6 b. This facilitates the axial adjusting movement of the cam sleeve 3 because of the intermediate space 28 forming in the axial region 22 between the carrier shaft 2 and the cam sleeve 3.

In a simplified variant of the example of the FIGS. 1 and 2, the opening 12 can be formed as a through-bore, wherein the support element 13 arranged in the through-bore is firmly connected to the cam sleeve 3 by means of a press connection, in particular by means of a press fit, and thus arranged fixed in position relative to the same.

FIG. 3 is a detail view of the first receiving groove 6 both according to the example of FIG. 1 and also according to the example of FIG. 2. According to the FIGS. 1 to 3, the two receiving grooves 6 a, 6 b can each comprise a groove base 23 c and a first and a second groove flank 23 a, 23 b. Here, the respective first groove flank 23 a is arranged at a smaller axial distance to the respective other receiving groove 6 b, 6 a than the respective second groove flank 23 b.

According to FIG. 3, the two groove flanks 23 a, 23 b in the first receiving groove 6 a, 6 b, preferentially in both receiving grooves 6 a, 6 b, can each be arranged at a first or second acute angle α1, α2 to the radial direction R. As is clearly shown in FIG. 3, a first angular value w1 of the first acute angle al is greater than a second angular value w2 of the second acute angle α2. This facilitates the axial movement of the detent element 11 or of the detent ball 21 out of the respective first or second receiving groove 6 a, 6 b towards the other, i.e. second or first receiving groove 6 b, 6 a respectively. In the example, a depth T of the first receiving groove 6 a measured along the radial direction R amounts to maximally 10%, preferentially maximally 8% of the radius r of the carrier shaft 2.

The above explanations regarding the configuration of the first receiving groove 6 a apply mutatis mutandis also to the second receiving groove 6 b. 

1. A sliding cam system for an internal combustion engine, comprising: carrier shaft extending along an axial direction, at least one sleeve-shaped cam sleeve arranged on the carrier shaft radially outside and axially adjustable relative to the carrier shaft, the at least one sleeve-shaped cam sleeve including at least one cam profile, the carrier shaft and the at least one cam sleeve for the transmission of torque being non-rotatably connected to one another, the at least one cam sleeve being axially adjustable relative to the carrier shaft between a first axial position and at least one second axial position and axially fixable in a respective one of the first axial position and the at least one second axial position on the carrier shaft via a detent device wherein the detent device includes: a first receiving groove assigned to the first axial position and a second receiving groove assigned to the at least one second axial position, wherein the first receiving groove and the second receiving grooves are axially spaced apart from one another and each extend along an outer circumference of the carrier shaft, and a preload element disposed on the at least one cam sleeve, wherein the preload element preloads a detent element arranged between the carrier shaft and the at least one cam sleeve towards the carrier shaft, and wherein the detent element is received in the first receiving groove when the at least one cam sleeve is located in the first axial position and received in the second axial groove when the at least one cam sleeve is located in the at least one second axial position.
 2. The sliding cam system according to claim 1, wherein the preload element is a detent spring arranged in a receptacle disposed on the at least one cam sleeve and exerts a preload force on the detent element.
 3. The sliding cam system according to claim 1, further comprising a receptacle structured as an opening extending radially in the at least one cam sleeve and a support element received in the receptacle, wherein the preload element radially supports itself on the support element radially outside for generating a preload force.
 4. The sliding cam system according to claim 3, wherein: the opening is structured as a through-bore, and the support element present in the through-bore is firmly connected to the at least one cam sleeve via a press connection and arranged fixed in place relative to the at least one cam sleeve.
 5. The sliding cam system according to claim 3, wherein the support element includes an external thread, which for the radial adjustability of the support element engages in an internal thread provided on the opening formed complementarily to the external thread, such that the support element is radially adjustable relative to the at least one cam sleeve.
 6. The sliding cam system according to claim 3, wherein the support element is structured as a threaded pin.
 7. The sliding cam system according to claim 3, further comprising a sleeve-shaped housing delimiting a housing interior provided on the support element, wherein the preload element and the detent element are each at least partially received in the housing interior.
 8. The sliding cam system according to claim 7, wherein the support element, the preload element, the detent element and the sleeve-shaped housing are provided integrally as a unit.
 9. The sliding cam system according to claim 1, wherein the detent element is formed structured as a detent ball.
 10. The sliding cam system according to claim 1, wherein a radius of the carrier shaft is reduced in an axial region between the two first receiving groove and the second receiving grooves.
 11. The sliding cam system according to claim 1, wherein: the first receiving groove and the second receiving grooves each comprise a groove base and a first groove flank and second groove flank, wherein the respective first groove flanks have a smaller axial distance to the respective other receiving groove than the respective second groove flanks; and wherein in at least one of the first receiving groove and the second receiving groove the first groove flank and the second groove flanks are each arranged at a first acute angle and a second acute angle respectively to a radial direction, wherein a first angular value of the first acute angle is greater than a second angular value of the second acute angle.
 12. The sliding cam system according to claim 1, wherein a radially measured depth of at least one of the first receiving groove and the second receiving groove amounts to maximally 10%, of a radius of the carrier shaft.
 13. An internal combustion engine for a motor vehicle, comprising: at least one cylinder comprising a combustion chamber provided with an inlet valve for introducing fresh air into the combustion chamber and an exhaust valve for discharging exhaust gas out of the combustion chamber are provided, and at least one sliding cam system for controlling at least one of the inlet valve and the exhaust valve, the at least one sliding cam system including: a carrier shaft extending along an axial direction; at least one sleeve-shaped cam sleeve arranged on the carrier shaft radially outside and axially adjustable relative to the carrier shaft, the at least one sleeve-shaped cam sleeve including at least one cam profile; the carrier shaft and the at least one cam sleeve for the transmission of torque being non-rotatably connected to one another; the at least one cam sleeve being axially adjustable relative to the carrier shaft between a first axial position and at least one second axial position and axially fixable in a respective one of the first axial position and the at least one second axial position on the carrier shaft via a detent device, wherein the detent device includes: a first receiving groove assigned to the first axial position and a second receiving groove assigned to the at least one second axial position, wherein the first receiving groove and the second receiving groove are axially spaced apart from one another and each extend along an outer circumference of the carrier shaft and a preload element disposed on the at least one cam sleeve, wherein the preload element preloads a detent element arranged between the carrier shaft and the at least one cam sleeve towards the carrier shaft, and wherein the detent element is received in the first receiving groove when the at least one cam sleeve is located in the first axial position and received in the second axial groove when the at least one cam sleeve is located in the at least one second axial position.
 14. The internal combustion engine according to claim 13, wherein the preload element is a detent spring arranged in a receptacle disposed on the at least one cam sleeve and exerts a preload force on the detent element.
 15. The internal combustion engine according to claim 14, wherein the receptacle is structured as an opening extending radially in the at least one cam sleeve and a support element is received in the opening, wherein the detent spring radially supports itself on the support element radially outside for generating the preload force.
 16. The internal combustion engine according to claim 15, wherein the support element includes an external thread that engages an internal thread provided on the opening such that the support element is radially adjustable relative to the at least one cam sleeve.
 17. The internal combustion engine according to claim 15, further comprising a sleeve-shaped housing delimiting a housing interior provided on the support element, wherein the detent spring and the detent element are each at least partially received in the housing interior.
 18. The internal combustion engine according to claim 13, wherein the detent element is structured as a detent ball.
 19. The internal combustion engine according to claim 13, wherein a radius of the carrier shaft is reduced in an axial region between the first receiving groove and the second receiving groove.
 20. The internal combustion engine according to claim 13, wherein a radially measured depth of the first receiving groove and the second receiving groove amounts to 10% or less of a radius of the carrier shaft. 